This invention relates generally to microscopes, and more particularly to a digital imaging microscope having an eyepiece for viewing and a digital camera for the electronic transmission of a digitized image of a specimen to a monitor or computer.
Digital imaging microscopy relates to the capture in digitized form of a magnified image of a specimen, for live viewing on a monitor or for processing and archiving by a computer. In certain known digital imaging microscopy systems, there is a microscope unit that resembles a standard microscope by having a light source, a specimen stage, optics for collecting and directing a light beam reflected from or transmitted through the specimen, and an eyepiece mounted at the end of an attached tube. Unlike a standard microscope, a conventional digital imaging microscope typically has a port for receiving a digital camera. The port is typically at the top of the microscope casing in the vicinity of the eyepiece. Furthermore, the optics are adapted to use a beamsplitter to direct a determined portion of the light to the camera port. A coupling adapter and a phototube provide a suitable physical connection between the microscope and the camera. As the camera and the eyepiece share the same optics, the coupling adapter together with the phototube must be dimensioned, and particularly must be of sufficient length, such that the camera lens can effectively image the beam onto the photosensitive image sensor.
Cameras employing a charge coupled device (CCD) are suitable for use in digital imaging microscopy. In a camera equipped with a CCD detector, the magnified image is digitized within the CCD camera and is transmitted as either a digital signal to a computer or as an analog signal to a monitor. The computer may be programmed with dedicated image processing and archiving software.
An example of such a digital imaging microscope is described in U.S. Pat. No. 5,933,513 (Yoneyama et al.). A commercially available example of such a system is the LEICA DC 100 Digital Imaging System manufactured by Leica Microscopy Systems Ltd. This system includes a DC 100 digital camera, a MZ12 stereo-microscope and a standard Windows-based PC computer running TWAIN and QWin image processing and archiving software. The system also has a phototube with C-mount optical adapter that is used to physically connect the digital camera to an opening at the top of the microscope casing within some suitable focal range for the digital camera. An electrical cable extends from the camera and connects to the computer via a digital frame grabber located in the computer.
Both the Yoneyama and LEICA microscopes are not compact. In particular, both systems include lengthy phototubes in part to provide the necessary focal length such that a peripherally connected camera can image the beam onto the photosensitive CCD image sensor, and in part to allow for the insertion of other optical devices such as filters between the magnifier and the camera. Furthermore, as the camera in each of these systems is a discrete device separate from the microscope, the camera and any other peripherally connected optical devices must be carefully calibrated each time the camera is mounted to the microscope. Further, each device may require its own power cable and data transmission cables which may interfere with the effective or convenient operation of the microscope. Lastly, these systems allow the camera to capture only a small portion of the image viewable from the eyepiece. While the Yoneyama and LEICA microscopes may be adaptable for a variety of uses, they are also cumbersome to operate for the novice or intermediate microscopist.
Other known digital microscopy systems include an adapter for affixing a digital camera over the eyepiece of a conventional microscope. The main drawback of such systems is that direct viewing and digital imaging cannot occur at the same time.
The object of the present invention is to provide a relatively compact and relatively inexpensive digital imaging microscope having at least some of the following characteristics and, in a preferred embodiment, having all of them:
(1) a compact assembly of optical components;
(2) means to deliver all the available light from the specimen to the image detector thus maximizing the quality of the images produced;
(3) an integrated digital image detector which needs only be calibrated once;
(4) means to capture a relatively large portion of the image available from the magnifying objective lens, the captured image area being roughly equivalent to that viewable through the eyepiece;
(5) means to provide an electronic signal representing the captured image in both analog and digital form;
(6) a single power connector for all the system components; and
(7) a convenient means to connect power and data cables at the base of the assembly.
One embodiment of the invention provides a digital imaging microscope for viewing and capturing an image of a specimen. The elements of the preferred embodiment listed in this paragraph are conventional. The microscope assembly has a base, a hollow bent arm extending generally upward from the base, a light source located either in the base or attached to the arm, a stage for receiving a specimen to be viewed, an objective lens, an optical component housing in the vicinity of the top of the arm, and an eyepiece. The objective lens is mounted on the microscope on the underside of the upper part of the arm along an unimpeded optical path from the specimen. The objective lens may be one of several mounted in a carousel. The user sets the microscope""s magnification by rotating the carousel so that a selected objective lens is positioned over the specimen. The objective lens collects light transmitted through the specimen and transmits it to a beamsplitter located in the housing. The beamsplitter splits the light arriving from the objective lens into two beams. One beam is directed to the eyepiece and the second beam to a digital image detector.
In a conventional digital imaging microscope, the digital image detector is located outside the optical component housing within a camera that is attached as a separate device by means of an adapter and a phototube. The eyepiece provides a magnified virtual image of the specimen observable with the human eye and the digital image detector converts the magnified image of the specimen into an analog electronic signal.
According to the one aspect of the invention, a beamsplitter assembly, positive lens and an image detector are provided within the optical component housing. This provides a compact design.
The beamsplitter assembly holds a plurality of prisms in a tray which may slide transversely to allow the user to select a prism to control the division of light between the eyepiece and the digital image detector. Preferably, at least three prisms are provided. A suitable set of prisms comprises a splitting prism, which splits the light collected equally between the eyepiece and the digital image detector, a columnar prism, which transmits all of the available light to the digital image detector, and a reflecting prism, which reflects all of the light to the eyepiece. This arrangement enables the microscope to be operated in three distinct modes:
(1) a direct viewing mode, in which all light is directed to the eyepiece;
(2) a digital imaging only mode, in which all light is directed to the image detector; and
(3) a dual viewing mode where light is directed to both the eyepiece and the image detector.
This arrangement provides the user with considerable flexibility. Direct viewing mode provides best viewing through the eyepiece as the image is of maximum intensity. Digital imaging only mode maximizes the light intensity available for image detection. Dual viewing mode allows one person, possibly a teacher, to operate the microscope with the aid of the eyepiece, while a number of other viewers, possibly students in a class, can watch on a standard monitor or on computer screens.
The positive lens is interposed between the beamsplitter assembly and the digital image detector so that it focuses the light from the beamsplitter onto the image detector. The use of the positive lens permits the image detector to be mounted within the optical component housing in close proximity to the beamsplitter, while still imaging a substantial portion of the image viewable through the eyepiece. This arrangement facilitates a compact design. The positive lens may preferably be mounted so that it can slide vertically within the optical component housing thus providing a means to focus the image onto the digital image detector.
A suitable image detector is a CCD. The CCD sensor captures an image of the specimen and converts this to an analog electronic signal which is transmitted by signal wires and electrical connectors to one or more RCA or S-type ports and to an analog/digital converter. The output of the analog/digital converter is directed to a USB output port.
According to a second aspect of the invention, the analog/digital converter, power supply, output ports and other electronic components are preferably located in the microscope base contributing to a compact and efficient design, free of cable connections at other parts of the microscope.
A microphone may optionally be provided on the microscope. The microphone is connected electrically to the image detector. The audio output of the image detector is sent either as an analog signal to, for example, an RCA audio port or, after digitization by the analog/digital converter, to a USB port, both output ports being located in the microscope base.
According to another embodiment of the invention, the beamsplitter assembly holds a single splitting prism mounted over the aperture. This splitting prism divides the light from the objective lens into two parts, one passing by reflection to the eyepiece and the other by transmission to the digital image detector. A suitable splitting prism comprises a semi-pentagonal shaped splitting prism joined to a compensatory prism having a reflectance-to-transmission split ratio of 1:1.
According to another embodiment of the invention, the microscope provides a stereoscopic, magnified image viewable through a pair of eyepieces and the means to capture a magnified image of the specimen with a digital image detector. This embodiment is generally the same as the preferred embodiment with the revisions described below to accommodate stereoscopic viewing.
The stereoscopic microscope suitably comprises a pair of eyepieces each having an eyepiece tube and a lens. In this embodiment, the carousel holds pairs of objective lenses. The carousel may be rotated to place a selected pair of objective lenses beneath the aperture at the bottom of the optical component housing such that light arriving from the specimen may be collected by the lens pair and transmitted to the beamsplitter assembly. The beamsplitter assembly has a pair of reflecting prisms, both placed over the aperture. For stereoscopic viewing through the eyepieces, both reflecting prisms direct light arriving from the objective lenses to the eyepieces. For imaging with the image detector, one reflecting prism is moved out of the light path thus allowing a beam to pass to a mirror, through a right-angle prism and the positive lens to the digital image detector. As in the earlier-described embodiment, the positive lens makes it possible to position the digital image detector close to the positive lens while at the same time capturing a substantial portion of the image viewable by means of the eyepiece.
According to another embodiment of the invention, a pair of objective lenses is provided to magnify the image of the specimen for stereoscopic viewing through the two eyepieces together with a third objective lens to capture an image on a digital image detector, Separate apertures in the optical component housing are provided for each of the three objective lenses. The beamsplitter assembly has two prisms. One prism receives light arriving from two objective lenses and reflects these beams to the eyepieces. The second prism redirects the light collected by the third objective lens through a positive lens to the digital image detector. As in the earlier-described embodiment, the positive lens makes it possible to position the digital image detector close to the positive lens while at the same time capturing a substantial portion of the image viewable by means of the eyepiece.